This project is designed to study mechanisms of ion transport and the factors which control membrane permeability in nitochondria. A primary objective is to characterize monovalent cation transport in preparation for eventual isolation and reconstitution of transport proteins. Accordingly, we propose to study the kinetics of the Na/h and K/H exchangers: To determine their Km, Vmax, and ph profiles; to determine their cation selectivity; and to search for specific inhibitors. We also propose to study the relationships between uniport and antiport mechanisms for Na+ and K+ tranport; to determine the effects of Ca++ and Mg++ on these mechanisms and to determine whether Na/H and K/H exchange are mediated by the same transporter. The factors controlling anion uniport will be studied. The effects of anesthetics on mitochondrial ion transport will uniport will be defined, and the mechanisms of action will be studied. We will examine effects of adenine and pyridine nucleotides on ion transport. These studies will be carried out in intact liver mitochondria and submitochondrial particles using ion electrodes, radioisotopes, atomic absorption spectroscopy and high pressure liquid chromatolgraphy. K+ is the major cation of the cell, and K+ transport in mitochondria is intimately connected with oxidative phosphorylation. I have postulated that the K/H exchanger is modulated through reversible inhibition by Mg++ ions and that this interaction provides a dynamic, finely tuned mechanism for matrix volume homeostasis in vivo. Futile cycling of K+ leads to heat production, and it is possible that this Mg++ braking mechanism is involved in obesity and other metabolic disorders. Hormones such as glucagon are known to affect mitochondrial K+ in vivo, and it is possible that the delicate balance of the mitochondrial K+ cycle is distrubed by pathophysiological processes. Mechanisms of mitochondrial cation transport are poorly understood; this project is designed to correct this deficiency by integrating cation transport mechanisms with current progress in bioenergetics and metabolism.